Lubricating composition and method for the hot extrusion of metals



y 1963 R. w. TOMBAUGH 3,096,881

M5500 FOR LUBRICATING COMPOSITION AND THE EXTRUS OF ME d Dec. 1956WITNESSESI INVENTOR Roy W Tombaugh BWMQQQ @Mwm BK United States PatentOffice 3 ,ll9fi,88l Patented July 9, 1963 3,096,881 LUBRICATINGCOMPOSITION AND METHOD FOR THE HOT EXTRUSION F METALS Roy W. Tombaugh,Bethe! Borough, Pa., assiguor to Westinghouse Electric Corporation, EastPittsburgh,

Pa., a corporation of Pennsylvania Filed Dec. 20, 1956, Ser. No. 629,6353 Claims. (Cl. 207-10) This invention relates to the hot extrusion ofmetals and particularly to a lubricating composition to be employed inlubricating the surfaces of heated metal billets to facilitate extrusionthrough or between dies.

Many metals and alloys in use can only be extruded satisfactorily atelevated temperatures. As is well known in the art, many metals, evenwhen highly heated, do not flow and shape readily in the dies of anextrusion press, and require unusually high pressures to producesatisfactory extrusions.

In the hot extrusion of metals, it would be .desirable to dispose somelubricating composition between the metal billet and the die. When themetal is deformed by an extrusion operation, it is subjected to aconsiderable stretching and thinning out action that is accompanied by aconsiderable flowing of the metal in various directions. This movementof metal takes place under high pressure, and a satisfactory lubricantshould control this flow and minimize or prevent metal-to-metal contactbetween the metal billet and the die.

The lubricating composition employed in the hot extrusion of metals mustbe incombustible at the extrusion temperature employed and must not bedestroyed or otherwise adversely afiected in the relatively brief periodinvolved in the extrusion process so as to render it useless as alubricant.

The object of this invention is to provide a lubricating composition forhot extrusion of metal comprising intermingled finely divided molybdenum.disulfide and finely divided lead.

Another object of this invention is to provide for the hot extrusion ofmetals by employing as a lubricant between a highly heated billet of themetal and the extrusion die a composition comprising finely dividedmolybdenum disulfide and finely divided lead.

Other objects of this invention will, in part, be obvious and will, inpart, appear hereinafter. For a better understandin of the nature andobjects of the invention, reference should be had to the followingdetailed description and drawing, in which the single FIGURE is acrosssection through a portion of a hot extrusion press.

It has been proposed to employ finely divided molybdenum .disulfidealone as a lubricant for the hot extrusion of metals. However, whensubjected to the high temperatures encountered in the hot extrusion ofmetal, molybdenum disulfide oxidizes readily and loses its lubricity,and in fact becomes abrasive.

In accordance with this invention, unexpected results have been obtainedin lubricating dies, particularly dies employed in the hot extrusion ofmetals, by applying thereto a lubricating composition comprisingintimately admixed finely divided molybdenum disulfide and finelydivided lead.

The lubricating composition of this invention is prepared by thoroughlyadmixing one part of finely divided molybdenum disulfide and from twoparts to six parts of finely divided lead, all parts being by volume.The molybdenum disulfide is preferably of a fineness to pass through asieve having from 100 to 500 meshes per lineal inch and the lead is of afineness to pass through a sieve having from 50 to 400 meshes to thelineal inch. This mixture can be employed in dry form. However, it ispreferred to add to the mixture a suitable organic liquid to form apaste. Suitable organic liquids that. may be employed are thepolyalkyleneglycols, such as polyethyleneglycol; liquid polyesters, suchas the esters of azelaic acid, adepic acid and the like; glycols; andpetroleum oil. Organic liquids having a viscosity of up to 1000centipoises at 25 C. can be satisfactorily employed, although it ispreferred to use those having a viscosity of not above centipoises at 25C. In paste form, the composition is more easily and readily applied tothe surfaces to be lubricated. Pastes having a viscosity of from 200 to100,000 centipoises at 25 C. have been found satisfactory.

In carrying out the extrusion process of this invention, the surface ofthe die that makes contact with the metal billet during extrusion iscoated with a thin layer of a paste comprising the lubricatingcomposition of the invention. To provide for the most completelubrication .during the extrusion process, it is also desirable to applya layer of the lubricating composition to the bore of the extrusioncontainer.

The metal billet is prepared'for extrusion by heating it to the desiredtemperature either in a furnace or a salt bath. It has been found thatheating the billet in a salt bath in such a manner so as to retainthereon a thin layer of molten salt is a satisfactory procedure. Theheated billet is introduced into the bore of the extrusion container andextruded under pressure by applying a ram or plunger to the end of thebillet, by conventional methods.

For many metals, it has also been found necessary to heat the metalbillet to a temperature of from 1500" F. to 2400 F. At this temperature,the billet, during the extrusion process, readily melts the leadcomponent of the lubricating composition. The molten lead cooperateswith the molybdenum disulfide to produce a composition having unusuallubricity. The extrusion container is maintained at a temperature ofabout 750 F. during the extrusion process so that the heated billet willnot cool too rapidly. The molybdenum disulfide exhibits excellentlubricating qualities at these high temperatures when associated withmolten lead.

Referring to the single FIGURE of the drawing, there is shown a metalbillet being extruded through a die in accordance with this invention.As shown in the single FIGURE, 3. layer 10 of the lubricatingcomposition of this invention has been applied to a bore 12 of anextrusion container 14 and also to that surface of an opening 16 of adie 18 that makes contact with a billet 20 as it is being extruded toform an extruded member 22. The portion of the extrusion press shown isconventional, the pressure required to extrude the billet being appliedby a ram 26 which may be hydraulically operated. A dummy block 24 isshown positioned between the billet 20 and the ram 26.

Metals of the following type have been successfully extruded byemploying as a lubricant the composition of this invention: uraniumalloys such as Ul2 Mo, (12% molybdenum-88% uranium); U-IO Nb; uraniuma1- loys of the type U-3.8 Si; and zirconium base alloys. The extrusionof carbon steel, stainless steel and titanium is facilitated greatly bythe lubricant of this invention. The surfaces of the extruded membershave been practically striation-free. Furthermore, the excellentlubricity provided by the lubricating composition has provided longerlife for the extrusion dies than heretofore possible.

Another important feature of the lubricating composition of thisinvention is that it permits the use of lower extrusion pressuresthereby making it possible to increase the reduction in area of themetal billet being extruded.

The following example illustrates the preparation of a thin pastecomprising the lubricating composition of this invention:

Example I Eight pants by volume of lead of a fineness of about 200 meshwas thoroughly admixed with 2 parts by volume of molybdenum disulfide ofa mesh of about 230. One part by volume of polyethyleneglycol wasthoroughly ad-. mixed with this mixture. A paste Was formed which had aviscosity of about 5000 centipoises at 25 C.

The following examples illustrate the excellent lubricity of thelubricating composition of this invention in the hot extrusion of metalsas compared to other known lubricating compositions.

Example II On a 500 ton horizontal extrusion press, twenty jacketedbillets having a diameter of about 2.55 inches and a length of about 6.5inches were extruded from a container having a. bore of a diameter of2.6 inches and through a die having a circular opening therethrough of adiameter of inch. Prior to each extrusion procedure, the lubricatingpaste of Example I was applied to the surface of the bore and to thesurface of the die opening. Each jacketed billet was heated prior toextrusion to a temperature of about 1900 F. in a molten salt bathcomprising, by Weight, 85% barium chloride and 15% sodium chloride. Theextrusion container was maintained at a temperature of about 750 F.during the extrusion procedure.

The jacketed billets extruded comprised a core of a uranium base alloycomprising, by weight, 88% of uranium and 12% molybdenum; anintermediate layer of a zirconium base alloy comprising, by weight,about 1.4% of tin, about 0.10% of chromium, about 0.06% of nickel, about0.13% of iron, and the balance being zirconium with incidentalimpurities, and an exterior layer of mild steel. The diameter of thecore Was about 1.58 inches, the wall thickness of the intermediate layerwas about 0.47 inch, and the Wall thickness of the exterior steel layerwas about 0.015 inch.

The average starting pressure required for the twenty extrusions was 405tons. The resistance to deformation K, also termed the extrusionconstant, stated in pounds per square inch was 42,800. The resistance todeformation, K is represented by the formula The die employed in ExampleII was replaced by a new die of same size and opening. Twenty-fourjacketed billets of the same size and composition of Example II wereextruded following the procedure and conditions as set forth in ExampleII. The lubricating composition, however, was replaced by a lubricatingpaste comprising finely divided lead alone dispersed inpolyethyleneglycol, the viscosity of the paste being about the same asExample I. The average starting pressure required for the twenty-fourextrusion was 496 tons. The pressure required to extrude the 'billets asrepresented by the extrusion constant K was 52,500 p.s.i. All extrudedmembers were heavily striated.

It will benoted that in Example II there is an 18' /2% reduction in theextrusion constant K over that of Example III. Such a reduction willmake it possible to increase the reduction in area of a billetapproximately by the use of the lubricating composition of thisinvention.

Finely divided graphite dispersed in petroleum oil was also employed asa lubricant for comparative purposes and it was found to be greatlyinferior to;the lubricant of finely divided lead in polyethyleneglycolemployed in Example II.

The lubricants of this invention have proven to be highly superior toany lubricant previously known in the ant of hot extrusion.

Since certain changes may be made in the above invention and difierentembodiments of the invention may be made withoutdeparting from the scopethereof, it is intended thatall matter contained in the abovedescription and drawing shall be interpreted as illustrative and not ina limiting sense.

I claim as my invention:

1. In the method of extruding a metal billet from an extrusion containerhaving a bore therethroug-h to accommodate the metal billet and adie atone end of the bore, the die having an opening through which the billetis extruded, the steps comprising applying a layer of a lubricatingcomposition consisting essentially of, by volume, 1 part of finelydivided molybdenum disulfied and from 2 parts to 6 parts of finelydivided lead to the surface of the bore and to the surfaces of the diewith which the billet makes contact during extrusion, heating the billetto a temperature of from 1500 F. to 2400 F. and introducing it into thebore of the extrusion container and extruding the billet under pressure.

2. A lubricating composition for use in the hot extrusion of metals,said composition consisting essentially of, by volume, one part offinely divided molybdenum disulfide and from 2 parts to 6 parts offinely divided lead.

3. A lubricating composition for use in the hot extrusion of metals,said composition consisting essentially of one part by volume of finelydivided molybdenum disulfide, from 2 parts to 6 parts by volume offinely divided lead, and an amount of an organic liquid sufficient toprovide a paste having a viscosity of from 200 to 100,000 centipoises at25 C.

References Cited in the file of this patent UNITED STATES PATENTS2,156,803 Cooper et al May 2, 1939 2,321,203 Henry et al June 8, 19432,361,211 Kalischer Oct. 24, 1944 2,385,144 Lorant Sept. 18, 19452,543,741 Zweifel Feb. 27, 1951 2,578,585 Orozco et a1 Dec. 11, 19512,588,625 Ferner et a1 Mar. 11, 1952 2,696,378 Kritscher Dec. 7, 19542,737,293 Beliveau Mar. 6, 1956 2,806,596 Dodds et al. Sept. 17, 19572,815,560 Buxton Dec. 10, 1957 FOREIGN PATENTS 564,046 Great BritainSept. 11, 1944 624,466 Great Britain June 9, 1949 102,917 Germany May29, 1899 OTHER REFERENCES The Extrusion of Titanium, by A. M. Sabrolf,W. M.v

Parris, and P. D. Frost, WADC Technical Report 54-555, March 1955, pp. 2and 3.

Metallurgy of the Rarer Metals No. 2; Zirconium, by G. L. Miller,Buttersworth Scientific Pub. (London), 1954. Lubrication in the Drawingof Metals, by Samuel Spring, 1945, 3rd. full pan, col. 1, p. 13.

1. IN THE METHOD OF EXTRUDING A METAL BILLET FROM AN EXTRUSION CONTAINERHAVING A BORE THERETHROUGH TO ACCOMMODATE THE METAL BILLET AND A DIET ATONE END OF THE BORE, THE DIE HAVING AN OPENING THROUGH WHICH THE BILLETIS EXTRUDED, THE STEPS COMPRISING APPLYING A LAYER OF A LUBRICATINGCOMPOSITION CONSISTING ESSENTIALLY OF, BY VOLUME, 1 PART OF FINELYDIVIDED MOLYBDENUM DISULFIED AND FROM 2 PARTS TO 6 PARTS OF FINELYDIVIDED LEAD TO THE SURFACE OF THE BORE AND TO THE SURFACES OF THE DIEWITH WHICH THE BILLET MAKES CONTACT DURING EXTRUSION, HEATING THE BILLETTO A TEMPERATURE OF FROM 1500*F. TO 2400*F. AND INTRODUCING IT INTO THEBORE OF THE EXTRUSION CONTAINER AND EXTRUDING THE BILLET UNDER PRESSURE.